For example, in a conventional passenger vessel, in general, a compartment having multilayered decks is provided in a hull, and a ramp way configured to connect between the decks each layer is provided in each compartment. In this case, residence compartments are formed in an upper layer of the hull, and vehicle compartments are formed in a lower layer, and a driver drives a car to enter the deck in the vessel from a quay wall via a shore ramp way, and moves the car to the deck of the lower layer via the ramp way to park at a specified position.
In addition, in such a passenger vessel, apart from the residence compartments and the vehicle compartments, a plurality of rooms such as an engine room and a shaft room are divided in the vessel. In this case, as international rules for vessels, the requirements of damage stability are defined and are also reflected in the Japanese domestic law. In the rules, as requirements of the vessel side damage, securement of residual restoring force after damage, and a hull inclination angle and the like are defined.
In addition, there is a compartment structure of the conventional vessel as described in Patent Literature 1 below. In an automobile carrier described in Patent Literature 1, a watertight deck of a lowest layer forming a void space in a bottom of the vessel is provided with a remotely openable seawater introducing means. Thus, when a vessel side outer plate of the vessel or the like is damaged and seawater enters the vessel, by opening the seawater introducing means provided in the watertight deck of the lowest layer, the seawater entered the vessel is introduced into the void space, the void space is allowed to function as a seawater ballast tank, and thus, it is possible to recover the restoring force of the vessel.